Kisiala, Anna AK

The study examines the phytochemical and phytohormone profiles of two ecotypes of Doliocarpus dentatus (Capadulla) from Guyana with an emphasis on their potential therapeutic applications, particularly in the context of erectile dysfunction. The research concentrates on the red and white ecotypes, which are visibly differentiated by the colouration of their inner and outer bark; moreover, the red ecotype is widely regarded by traditional knowledge to be more efficacious in treating erectile dysfunction. The study seeks to provide much-needed scientific evidence to support the traditional medicinal uses of D. dentatus and aims to accomplish this by providing semi-targeted and targeted analysis of its bioactive compounds.The thesis employs a multi-faceted approach, commencing with Chapter 2, an examination of the international and national frameworks that govern natural product research in Guyana, thereby ensuring ethical and sustainable practices. Chapter 3, Liquid chromatography-mass spectrometry-based metabolomics was utilized to analyze the phytochemical profiles of the red and white ecotypes of D. dentatus. Approximately 847 compounds were identified, with 138 tentatively classified as potentially therapeutic, particularly polyphenols exhibiting antioxidant properties. Chapter 4 focus on the phytohormone profiling revealed that the red ecotype generally exhibited higher levels of active cytokinins, particularly trans-zeatin (tZ) and cis-zeatin (cZ), compared to the white ecotype. A strong correlation was identified between specific cytokinins and secondary metabolites such as flavonoids and alkaloids, suggesting complex interactions that may enhance the therapeutic potential of D. dentatus. Chapter 5 further analysis of total phenolic content, flavonoid content, and their antioxidant capacities demonstrated differences between the red and white ecotypes, with the red ecotype generally showing higher levels of these compounds. Both ecotypes demonstrated significant antioxidant activity, with the red ecotype showing enhanced radical scavenging capacity. The study also revealed a diverse range of bioactive compounds, including flavonoids, terpenoids, and alkaloids, which may contribute to the plant's reported medicinal properties. This semi-targeted and targeted analysis provides novel insights into the phytochemical and phytohormone profiles of D. dentatus ecotypes, offering a scientific basis for their traditional medicinal uses and potential therapeutic applications. The findings suggest that D. dentatus, particularly the red ecotype, may have significant potential for developing new drugs, especially in the context of erectile dysfunction therapy.

Author Keywords: antioxidant, Bioactive compounds, liquid chromatography-electrospray ionization tandem mass spectrometry, metabolomics, secondary metabolites, therapeutic properties